break-on-url-match-monkeypatch.js

/* Call a function when a fetch is made to a URL containing `str`
 * @param {String} str          if a URL being fetched contains this string, call {@param callback}
 * @param {Function} callback   a function to call when a fetch is made to the given {@param str}
 * @example <caption>Call debugger on fetches to `example.com`</caption>
 *
 * breakOnUrlMatch('example.com', () => { debugger; });
 */
function breakOnURLMatch(str, callback) {
       let nextOpen = XMLHttpRequest.prototype.open;
       XMLHttpRequest.prototype.open = function monkeypatchedOpen(...args) {
               let url = args[1];
               if (url && url.indexOf(str) >= 0) { callback(); }
               console.log('XHR for ', url);
               return nextOpen(...args);
       }

       let nextFetch = window.fetch;
       window.fetch = function monkeypatchedFetch(...args) {
               let url = args[0];
               if (url && url.indexOf(str) >= 0) { callback(); }
               console.log('Fetch for ', url);
               return nextFetch(...args);
       }
}